Possible chemical signals of pulmonary embolism will be investigated. BIBLIOGRAPHIC REFERENCES: Silverstein, E. and Friedland, J.: Lack of elevation of angiotensin converting enzyme in Freund's adjuvant granuloma in the rat. Fed. Proc. 35, 717, no.2820, 1976. Silverstein, E. and Friedland, J.: Elevated serum and spleen angiotensin converting enzyme and serum lysozyme in chronic Gaucher's disease. Clin. Res. 24, 478A, 1976.